Multi-function slurry delivery system

ABSTRACT

A method and system for delivering a mixed slurry for use chemical mechanical polishing operation. A first slurry may be mixed with a second slurry to provide a mixed slurry thereof. A flow rate and a mixing ratio associated with the mixed slurry can be controlled to provide an accurate flow rate control and adjustable mixing ratio thereof. The first slurry and the second slurry may be mixed in-line utilizing an in-line mixing mechanism to provide a mixed slurry thereof. Alternatively, the first and second slurries may be pre-mixed utilizing a pre-mixing mechanism to provide a mixed slurry there.

TECHNICAL FIELD

The present invention relates generally to semiconductor fabricationmethods and systems. The present invention also generally relates tochemical mechanical polishing (CMP) devices and techniques thereof. Thepresent invention additionally relates to slurry delivery methods andsystems.

BACKGROUND OF THE INVENTION

Integrated circuits are typically formed on substrates, particularlysilicon wafers, by the sequential deposition of conductive,semiconductive or insulative layers. After each layer is deposited, thelayer is etched to create circuitry features. As a series of layers aresequentially deposited and etched, the outer or uppermost surface of thesubstrate, i.e., the exposed surface of the substrate, becomessuccessively more non-planar. This occurs because the distance betweenthe outer surface and the underlying substrate is greatest in regions ofthe substrate where the least etching has occurred, and least in regionswhere the greatest etching has occurred. With a single patternedunderlying layer, this non-planar surface comprises a series of peaksand valleys wherein the distance between the highest peak and the lowestvalley may be the order of 7000 to 10,000 Angstroms. With multiplepatterned underlying layers, the height difference between the peaks andvalleys becomes even more severe, and can reach several microns.

This non-planar outer surface presents a problem for the integratedcircuit manufacturer. If the outer surface is non-planar, then photolithographic techniques used to pattern photoresist layers might not besuitable, as a non-planar surface can prevent proper focusing of thephotolithography apparatus. Therefore, there is a need to periodicallyplanarize this substrate surface to provide a planar layer surface.Planarization, in effect, polishes away a non-planar, outer surface,whether conductive, semiconductive, or insulative, to form a relativelyflat, smooth surface. Following planarization, additional layers may bedeposited on the outer surface to form interconnect lines betweenfeatures, or the outer surface may be etched to form vias to lowerfeatures.

Chemical mechanical polishing is one accepted method of planarization.This planarization method typically requires that the substrate bemounted on a carrier or polishing head, with the surface of thesubstrate to be polished exposed. The substrate is then placed against arotating polishing pad. In addition, the carrier head may rotate toprovide additional motion between the substrate and polishing surface.Further, a polishing slurry, including an abrasive and at least onechemically-reactive agent, may be spread on the polishing pad to providean abrasive chemical solution at the interface between the pad andsubstrate.

Important factors in the chemical mechanical polishing process are: thefinish (roughness) and flatness (lack of large scale topography) of thesubstrate surface, and the polishing rate. Inadequate flatness andfinish can produce substrate defects. The polishing rate sets the timeneeded to polish a layer. Thus, it sets the maximum throughput of thepolishing apparatus.

Each polishing pad provides a surface, which, in combination with thespecific slurry mixture, can provide specific polishing characteristics.Thus, for any material being polished, the pad and slurry combination istheoretically capable of providing a specified finish and flatness onthe polished surface. The pad and slurry combination can provide thisfinish and flatness in a specified polishing time. Additional factors,such as the relative speed between the substrate and pad, and the forcepressing the substrate against the pad, affect the polishing rate,finish and flatness.

For the development of chemical mechanical polishing technology in the0.13 um range and beyond, a number of challenges must be overcome,particularly in light of slurry delivery systems. In order evaluate newtypes of slurries, it is necessary to control the flow rate of suchslurries and the mixing ratios of newly mixed slurries. To date, aneffective method and system for controlling slurry flow rate and mixingratios has not been achieved. In addition, an effective slurry flow ratecontrol and mixing ratio method and system is necessary to massproduction applications. The present inventors have concluded, based onthe foregoing, that a need exists for a new method and system forcontrolling slurry flow rate and mixing ratios thereof.

BRIEF SUMMARY OF THE INVENTION

The following summary of the invention is provided to facilitate anunderstanding of some of the innovative features unique to the presentinvention, and is not intended to be a full description. A fullappreciation of the various aspects of the invention can be gained bytaking the entire specification, claims, drawings, and abstract as awhole.

It is therefore one aspect of the present invention to provide animproved semiconductor fabrication method and system.

It is therefore another aspect of the present invention provide animproved method and system for delivering a slurry utilized in achemical mechanical polishing operation.

It is still another aspect of the present invention to provide in-linemixing for and accurate control of flow rates of slurries utilized inchemical mechanical polishing operations.

It is yet another aspect of the present invention to provide pre-mixingfunctions, including accurately controlled rates thereof, for slurriesutilized in chemical mechanical polishing operations.

The above and other aspects of the present invention can thus beachieved as is now described. A method and system for delivering a mixedslurry for use in a chemical mechanical polishing operation is disclosedherein. According to the present invention described herein, a firstslurry may be delivered for use in a chemical mechanical polishingoperation. The first slurry may be mixed with a second slurry to providea mixed slurry thereof. A flow rate and a mixing ratio associated withthe mixed slurry can be controlled to provide an accurate control of theflow rate and adjustable mixing ratios for use in enhanced chemicalmechanical polishing operations utilized in the fabrication ofsemiconductor devices.

The first slurry and the second slurry may be mixed in-line utilizing anin-line mixing mechanism to provide a mixed slurry thereof. In anin-line mixing scenario, the mixing ratio may be adjusted by controllingthe flow rate of the mixed slurry and/or the first slurry and/or secondslurry. Alternatively, the first and second slurries may be pre-mixedutilizing a pre-mixing mechanism to provide a mixed slurry there. In apre-mixing scenario, the mixing ratio may be adjusted by measuring theweight of the first slurry and/or the second slurry. The pre-mixingmechanism may comprise a pre-mixing tank, such that the pre-mixing tankis associated with at least one load cell to control the mixing ratio.

The flow rate of the mixed slurry delivered from the pre-mixing tank toa chemical mechanical polishing device can be controlled utilizing aslurry pump associated with the pre-mixing tank. The mixed slurry canthereafter be delivered to the chemical mechanical polishing deviceand/or systems thereof. The pre-mixing mechanism and the in-line mixingmechanism may be integrated into a multi-function slurry delivery systemand/or device. The first slurry can be delivered from a first supplytank linked to at least one circulation pump, wherein the circulationpump is operable in association with at least one slurry pump. Thesecond slurry can be delivered from a second supply tank connected to atleast one circulation pump, wherein the second supply tank is operablein association with at least one slurry pump. The first and secondsupply tanks are operable in association with at least one valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form part of the specification,further illustrate the present invention and, together with the detaileddescription of the invention, serve to explain the principles of thepresent invention.

FIG. 1 depicts a block diagram illustrating a multi-function slurrydelivery system, in accordance with a preferred embodiment of thepresent invention; and

FIG. 2 illustrates a high-level block diagram illustration amulti-function slurry delivery system, in accordance with a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The particular values and configurations discussed in these non-limitingexamples can be varied and are cited merely to illustrate embodiments ofthe present invention and are not intended to limit the scope of theinvention.

FIG. 1 depicts a block diagram illustrating a multi-function slurrydelivery system 10, in accordance with a preferred embodiment of thepresent invention. System 10 generally includes a first supply tank 12and a second supply tank 14. Supply tank 12 can contain a slurry A,while supply tank B can contain a slurry B. Supply tank 12 is connectedto a circulation pump 16. Supply tank 14 is generally connected to acirculation pump 18. Circulation pump 16 is connected to supply tank 12by lines 17 and 13 through which a slurry may flow.

A slurry may thus enter supply tank 12 though line 12 and exit throughline 17. A valve 32 is situated between circulation pump 16 and adelivery pump 20 on line 33. Line 33 is connected to line 13. A line 37connects delivery pump 20 to an in-line mixing mechanism 30, which canbe utilized to control the flow rate and mixing ratio of a slurry beingmixed via in-line mixing mechanism 30. In-line mixing mechanism 30 inturn can deliver a slurry (e.g., a mixed slurry) to a chemicalmechanical polishing device 38 or system thereof through line 29.In-line mixing mechanism is additionally connected to a delivery pump 22by a line 23 through which a slurry may flow.

Delivery pump 22 is connected to a line 41 which is connected to a valve36, which in turn is connected to a line 15 that is connected to a line19. Line 19 connects circulation pump 18 to supply tank 14 (i.e., secondsupply tank). Slurry can be delivered to supply tank 14 through line 19and can exit supply tank 14 through a line 21, which in turn isconnected to circulation pump 18. A line 46 is connected to line 19.Line 46 is connected to a valve 38, which in turn is connected to a line48. Line 48 is connected to a pre-mixing mechanism 24, which can beconfigured as a pre-mixing tank.

Pre-mixing mechanism 24 is associated with one or more load cells 40,42, and 44. Pre-mixing mechanism 24 is additionally connected to a line49 which can deliver slurry (i.e., pre-mixed slurry) to a delivery pump26 which in turn can deliver the slurry via a line 47 to chemicalpolishing device 28. Delivery pump 26 can be utilized to control theflow rate of a slurry being mixed in pre-mixing mechanism 24. The mixingratio of the slurry delivered via pre-mixing tank 24 can be adjusted bymeasuring the slurry's weight.

One or more load cells 40, 42 and 44 can be utilized to control themixing ratio of the slurry being mixed in pre-mixing mechanism 24.Slurry can enter pre-mixing mechanism 24 through line 48 or a line 43.Line 43 is connected to a valve 34 which in turn is connected to a line35 that is connected to line 13. A slurry can thus be delivered directlyto chemical mechanical polishing device 28 from first supply tank 12 orsecond supply tank 14.

FIG. 2 illustrates a high-level block diagram illustration amulti-function slurry delivery system 50, in accordance with a preferredembodiment of the present invention. Note that system 50 of FIG. 2 isanalogous to system 10 of FIG. 1. System 50 generally includes anin-line mixing mechanism 52 and a pre-mixing mechanism 54. In-linemixing mechanism 52, as indicated at block 56, permits a slurry mixingratio to be adjusted by controlling the flow rate of the slurry.Pre-mixing system 54, as indicated at block 58, permits a mixing ratioof the slurry to be adjusted by measuring the weight of the slurry.In-line mixing mechanism 52 of FIG. 2 is generally analogous to in-linemixing mechanism 30 of FIG. 1. Pre-mixing mechanism 54 of FIG. 2 isgenerally analogous to pre-mixing mechanism 24 of FIG. 1.

Pre-mixing mechanism 52 can thus be implemented separately or togetherwith pre-mixing tank 54 to form system 50. System 50 provides aninnovative process capability with in-line and pre-mixing functions inone recipe. System 50 can supply slurry to a varying CMP tools and iscompatible with a variety of CMP processes (e.g., W, STI, ILD, Cu, etc).System 52 can be easily applied to mass production scenarios andoperations, and can solve the slurry contamination problem caused by theuse of central supply systems. System 52 can also provide a local supplysystem for every CMP machine or device currently in use in industry.

Based on the foregoing, it can thus be appreciated that FIG. 1 and FIG.2 generally describe a method and system for delivering a mixed slurryfor use in a chemical mechanical polishing operation is disclosedherein. According to the present invention described herein, a firstslurry may be delivered for use in a chemical mechanical polishingoperation. The first slurry may be mixed with a second slurry to providea mixed slurry thereof. A flow rate and a mixing ratio associated withthe mixed slurry can be controlled to provide an accurate control of theflow rate and adjustable mixing ratios for use in enhanced chemicalmechanical polishing operations utilized in the fabrication ofsemiconductor devices.

The first slurry and the second slurry may be mixed in-line utilizing anin-line mixing mechanism (e.g., in-line mixing mechanism 42) to providea mixed slurry thereof. In an in-line mixing scenario, the mixing ratiomay be adjusted by controlling the flow rate of the mixed slurry and/orthe first slurry and/or second slurry. Alternatively, the first andsecond slurries may be pre-mixed utilizing a pre-mixing mechanism (e.g.,pre-mixing mechanism 24) to provide a mixed slurry there. In apre-mixing scenario, the mixing ratio may be adjusted by measuring theweight of the first slurry and/or the second slurry. The pre-mixingmechanism may comprise a pre-mixing tank, such that the pre-mixing tankis associated with at least one load cell to control the mixing ratio.The pre-mixing tank may also be connected to at least one delivery pumpvia a slurry line (e.g., line 49). Such a delivery pump (e.g., deliverypump 26) can permit a slurry to be pumped to a chemical mechanicalpolishing devices.

The flow rate of the mixed slurry delivered from the pre-mixing tank toa chemical mechanical polishing device can be controlled utilizing aslurry pump associated with the-pre-mixing tank. The mixed slurry canthereafter be delivered to the chemical mechanical polishing deviceand/or systems thereof. The pre-mixing mechanism and the in-line mixingmechanism may be integrated into a multi-function slurry delivery systemand/or device. The first slurry can be delivered from a first supplytank (e.g., supply tank 12) linked to at least one circulation pump,wherein the circulation pump is operable in association with at leastone slurry pump. The second slurry can be delivered from a second supplytank (e.g., supply tank 14) connected to at least one circulation pump,wherein the second supply tank is operable in association with at leastone slurry pump. The first and second supply tanks are operable inassociation with at least one valve.

The embodiments and examples set forth herein are presented to bestexplain the present invention and its practical application and tothereby enable those skilled in the art to make and utilize theinvention. Those skilled in the art, however, will recognize that theforegoing description and examples have been presented for the purposeof illustration and example only. Other variations and modifications ofthe present invention will be apparent to those of skill in the art, andit is the intent of the appended claims that such variations andmodifications be covered. The description as set forth is thus notintended to be exhaustive or to limit the scope of the invention. Manymodifications and variations are possible in light of the above teachingwithout departing from scope of the following claims. It is contemplatedthat the use of the present invention can involve components havingdifferent characteristics. It is intended that the scope of the presentinvention be defined by the claims appended hereto, giving fullcognizance to equivalents in all respects.

1. A method for delivering a mixed slurry for use in a chemicalmechanical polishing operation, said method comprising the steps of:delivering a first slurry for use in a chemical mechanical polishingoperation; mixing said first slurry with a second slurry to provide amixed slurry thereof; and controlling a flow rate and a mixing ratioassociated with said mixed slurry, thereby providing an accurate controlof said flow rate and adjustable mixing ratios thereof for use inenhancing chemical mechanical polishing operations utilized in thefabrication of semiconductor devices.
 2. The method of claim 1 whereinthe step of mixing said first slurry with said second slurry to providea mixed slurry, further comprises the step of: mixing said first slurrywith said second slurry in-line to provide a mixed slurry thereof. 3.The method of claim 2 further comprising the step of adjusting saidmixing ratio by controlling said flow rate.
 4. The method of claim 1wherein the step of mixing said slurry with said second slurry, furthercomprises the step of: pre-mixing said first slurry with said secondslurry to provide a mixed slurry thereof.
 5. The method of claim 4further comprising the step of: adjusting said mixing ratio by measuringa weight of said first slurry.
 6. The method of claim 4 furthercomprising the step of: adjusting said mixing ratio by adjusting aweight of said second slurry.
 7. The method of claim 4 furthercomprising the steps of: adjusting said mixing ratio by adjusting aweight of said first slurry and a weight of said second slurry.
 8. Themethod of claim 4 further comprising the steps of: pre-mixing said firstslurry and said second slurry in a pre-mixing tank to provide said mixedslurry, wherein said pre-mixing tank is associated with at least oneload cell to control said mixing ratio; controlling said flow rate ofsaid mixed slurry delivered from said pre-mixing tank to a chemicalmechanical polishing device utilizing a slurry pump associated withsaid-pre-mixing tank; and thereafter delivering said mixed slurry tosaid chemical mechanical polishing device.
 9. The method of claim 1wherein the step of mixing said slurry with said second slurry, furthercomprises the step of: mixing said first slurry with said second slurryin-line to provide a mixed slurry thereof; and pre-mixing said firstslurry with said second slurry to provide a mixed slurry thereof. 10.The method of claim 1 further comprising the step of: delivering saidfirst slurry from a first supply tank linked to at least one circulationpump, wherein said circulation pump is operable in association with atleast one slurry pump; and delivering said second slurry from a secondsupply tank connected to at least one circulation pump, wherein saidsecond supply tank is operable in association with at least one slurrypump; and wherein said first and second supply tanks are operable inassociation with at least one valve.
 11. A system for delivering aslurry for use in a chemical mechanical polishing operation, said systemcomprising: a first slurry for use in a chemical mechanical polishingoperation; a mixing mechanism for mixing said first slurry with a secondslurry to provide a mixed slurry thereof; and a control mechanism forcontrolling a flow rate and a mixing ratio associated with said mixedslurry, thereby providing an accurate control of said flow rate andadjustable mixing ratios thereof for use in enhancing chemicalmechanical polishing operations utilized in the fabrication ofsemiconductor devices.
 12. The system of claim 11 wherein said mixingmechanism further comprises: in-line mixing mechanism for mixing saidfirst slurry with said second slurry in-line to provide a mixed slurrythereof.
 13. The system of claim 12 wherein said control mechanismpermits said mixing ratio to be adjusted by controlling said flow rate.14. The system of claim 11 wherein said mixing mechanism furthercomprises: a pre-mixing mechanism for pre-mixing said first slurry withsaid second slurry to provide a mixed slurry thereof.
 15. The system ofclaim 14 wherein said mixing ratio is adjustable by measuring a weightof said first slurry.
 16. The system of claim 14 wherein said mixingratio is adjustable by measuring a weight of said second slurry.
 17. Thesystem of claim 14 wherein said mixing ratio is adjustable by adjustinga weight of said first slurry and a weight of said second slurry. 18.The system of claim 14 wherein: said pre-mixing mechanism furthercomprises a pre-mixing tank for pre-mixing said first slurry and saidsecond slurry to provide said mixed slurry, such that said pre-mixingtank is associated with at least one load cell to control said mixingratio; and said flow rate of said mixed slurry delivered from saidpre-mixing tank to a chemical mechanical polishing device iscontrollable utilizing a slurry pump associated with said-pre-mixingtank.
 19. The system of claim 11 wherein said mixing mechanism furthercomprises: in-line mixing mechanism for mixing said first slurry withsaid second slurry in-line to provide a mixed slurry thereof; andpre-mixing mechanism for pre-mixing said first slurry with said secondslurry to provide a mixed slurry thereof.
 20. The system of claim 11wherein said delivery mechanism further comprises: a first supply tankfor delivering said first slurry, wherein said first supply tank islinked to at least one circulation pump, such that said circulation pumpis operable in association with at least one slurry pump; a secondsupply tank for delivering said second slurry, wherein said secondsupply tank is connected to at least one circulation pump, such thatsaid second supply tank is operable in association with at least oneslurry pump; and wherein said first and second supply tanks are operablein association with at least one valve.